Magnetic compass



May-28, 1935. H. T. FAUS 2,003,179

MAGNETIC `COMPASS Filed oct. V12, 1933 Invenbov: Hamold T.' Paus,

His Att ohm.

Patented May 2.8, 1935 UNITED STATES MAGNETIC COMPASS Harold T. Faus, Lynn, Mass., assignor to General Electric Company, a corporation of New York Application October 12, 1933, Serial No. 693,279

8 Claims.

Myv invention relates to magnetic compasses and orienting devices and has for its principal object the provision of Compasses of increased sensitiveness and decreased tendency toward vibratiofn. Other and further objects and advantages will become apparent as the description proceeds.

In carrying out my invention in its preferred form, I utilize one or more composite bars of magnetic material as the magnetic directing element. The composite bars comprise a central portion of high permeability material and end portions of high coercive force material. In this manner, the magnetic leakage flux is concentrated at the ends of the composite bars and the central portions of the bars are easily machinable to permit mounting of jewels or bearings for pivoting. The compasses are preferably mounted in cups oi electrically conducting material coaxial with the pivot axis for the purpose of damping vibrations by the absorption oi the energy of vibration as eddy currents in the electrically conducting material.

The features of my invention which I believe to be novel and patentable will be pointed out in the claims appended hereto. A better understanding of my invention, itself, may be obtained by referring to the following description taken in connection with the accompanying drawing in which Fig. 1 is a plan view of one embodiment of my invention; Fig. 2 is an elevation, partially ln section, of the embodiment of Fig. 1; Fig. 3 is a 'plan view of the rotatable element in a modied form of my invention; Fig. 4 is a schematic circuit diagram illustrating the application of compasses made in accordance with my invention to the automatic steering of vessels; Fig. 5 is an elevation, partially in section, of a portion of the apparatus shown in Fig. 4; and Fig. 6 is a perspective view in part of another modified form of my invention designed to minimize vibration around axiorizontal axis as well as around the vertical a s. f

Referring now more in detail to the drawing in which like reference characters are used to designate like parts throughout, in the arrangement illustrated in Figs. l and 2, a magnetic compass is mounted in a suitable case I I having a suitable protective cover I2, preferably composed 50 of glass or other transparent material. The directing element, itself, comprises a composite bar I3 consisting of a central portion Il carrying magnetic bars I5. vThe bars I5 are composed oi magnetic material having a high` coercive force, such as, for example, cobalt steel containing approximately 46% cobalt, or a steel alloy containing approximately 6 to 15% aluminum, 20 to 30% nickel, and, in some cases, a certain amount of chromium in addition to iron. Such alloys may be prepared with coercive forces varying from 5 300 to 500 Gilberts per centimeter and even much higher. The central portion I4 is composed of magnetic material having a high permeability, for example, an alloy of nickel and iron containing approximately I'ISI/2% of nickel. 'I'his mal0 terial not vonly has high magnetic permeability but is relatively easily machined in comparison with any material which would be suitable for permanent magnets. For this reason, the expenseV of manufacture of the Compasses is considerably reduced since it is unnecessary to drill into hard steel for the purpose of mounting jewels or bearings or, in the alternative, it is unnecessary to go through the double process of machining the compass needles before hardening them, and then hardening them after the machining operation has been completed. By employing a material of high permeability for the central portion, only a small portion oi' the magnetizing force of the high coercive force end portions is required to keep the flux density in the central portion as high or higher than that in the end portions. In this manner, the composite needle acts as a single long magnet with the correspondingly low demagnetizing effect and high magnetic moment.. Likewise, the leakage iiux is concentrated in the ends oi the composite compass needle and increases the damping eiIect when the needle .is placed inside a ring of copper as will be explained hereinafter.

In the arrangement shown in Figs. 1 and 2, the high permeability pieces Il are provided at their outer ends with transverse projections I6, which may be bent up to grip the inner ends of the magnetized bars I5. II desired, the portions I6 may be so proportioned as to permit completely surrounding the bar I5 and, if desired, they may be increased somewhat in length to form tubular portions I1 receiving the bars I5, as shown in Fig. 6, in order to minimize leakage 4=5v or stray flux. The central portion I4 is pierced to form a circular opening I8 in which may be mounted a hollow cylindrical piece I9 carrying a, Jewel 20, or other suitable bearing, to cooperate with a conical pivot 2|. The hollow cylin- 50 drical piece I9 also carries a pointer 22 cooperating with a scale 23, the graduations oi which are not shown but which may be divided in degrees or in accordance with the well-known points of the compass.

l arrangement in which a separate pointer is employed and the magnetic element is mounted on a pivot, it lwill be understood that I am not limited to this exact arrangement. If desired, for expl a compass card of the type shown in Fig. 3 may be utilized instead of the pointer 22, or the composite bar i3, itself, may serve as the pointer. Likewise, any other desired rotatabie mounting may be employed, such as, for example, oating a movable element i3 with a card of the type shown in Fig. 3 in alcohol or other suitable uid contained in a cup 2li.

In order to minimize vibrations, the composite magnetic needle i3 is preferably mounted within a cup 2G, composed of electrically conducting material, substantially coaxial with the pivot 2l or the axis of rotation of the composite needle i3. As it will be readily understood by those skilled in the art, if the element i3 vibrates or -oscillates about the pivot 2l, the magnetic flux produced by the magnetized bars i5 will cut through portions of the metal of which the cup 20 is composed,v inducing electromotive forces therein which tend to produce eddy currents. The eddy currents inturn produce magnetic ux which reacts with the magnetized bars l5 to oppose the oscillatory motion of the needle i3, and the energy of oscillation is rapidly absorbed or dissipated by the eddy currents in the cup 243. In this manner, oscillation of the magnetic needle i3 is retarded. By means of this construction, I have succeeded in producing compasses which make not more than one and onehalf complete vibrations after being deected 90 and released. The reaction between the magnets i3 and the damping element 26 obviously overcomes oscillation about a horizontal ams transverse to the composite needle i3, as

well as about the vertical axis of the pivot 2l.

Although, in the arrangement shown in Fig. 2, I have disclosed L. ping element 26m the shape of a cup, it will be understood that a damping ring, which in the lower portion 25 is omitted, might also, if desired, be employed.

In the arrangement shown in Figs.' 1 and 2, I have illustrated the use of a single composite magnetic needle i3, but it will be understood that my invention is also applicable to magnetic compasses and orienting devices in which a plurality of magnetic needles are employed. For example, in the arrangement of Fig. 3, a plurality of composite needles i3' are mounted on a compass card 26. In the arrangement of Fig. 6. a plurality of magnetized bars l5 are mounted in a central element i4 composed of high permeability material which may, if desired; be in sheet form with lateral projecting portions rolled to form hollow cylindrical portions ll to receivel the vibrations of the rotatable element about its Y pivot axis or axis of rotation 2 l 2 l and its transverse horizontal axis T, T'. ploying a plurality of composite magnetic needles as shown in the arrangements of Figs. 3 and 6, I am also able to dampen vibrations about a 75, longitudinal horizontal axis, such as the axis However, by 4em-v notaire passes, particularly, this will obviously be advantageous.

In addition to direction indicating devices or compasses, my invention may also be applied to other apparatus employing direction responsive elements. For example, in the automatic steering apparatus disclosed in Figs. 4 and 5, a magnetic compass, constructed in accordance with my invention, is mounted on a ship or on aircraft so that the deiiecting pointer 22 is permitted to cooperate with a pair of contacts 28 and 23 carried by a rotatable mounting 33, which may be adjusted in angular position with respect te the fore and aft line of the ship or aircaft by means of any suitable device, such as the worm gear 3l. The deecting element 22 is arranged to control either directly or indirectly through contact 28 or 29 a steering motor 32 having a pair of oppositely connected eld windings 33 and 3G.' Direct current is supplied by source 35 and the steering motor 32 is mechanically connected through gearing 33 to a lever 3l connected to a rudder not shown.

,The rotatable mounting 30 is rotated so that the fore'and aft line 33, 33 of the vessel bears the desired angular relationship to the magnetic north-and-south line 39, 33 on the rotatable mountin 3U. 'Ihe line 39, 33' is obviously a magnetic no h-and-south line since, Whenever the vessel veers from its course, the deilecting pointer 22 makes contact with one or the other of contacts 23 and 23 so that the steering motor 32 is operated and the course is corrected so as to make the line 39, 33' follow the magnetic north y I and south. As will be readily understood, when contact is made between pointer 22 and contact 23, the circuit will be closed from the' source 35 through conductor 13, pointer 22, contact 28;co1- lector ring 6l, eld winding 3G, conductor Q2, back to source 35, starting the operation of steering motor 32 in a given direction. Likewise, when the pointer 22 makes contact with the contact 29, the circuit will be closed from the source 35 through eonductr et, pointer 22, Contact 2e, collector ring 33, iield winding 33, and conductor d2, back to source 35, starting the operation of the steering motor in the opposite direction.

While I have described my invention as embodied in concrete form and as operating in a specic manner in accordance with provisions of the patent statutes, it should be understood that I do not limit my invention thereto since various modications thereof ywill suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope of which is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A compass needle comprising a central por.- tion composed of magnetic material and end portions composed of a different magnetic material.

the material of which the central portion is composed being softer and more permeable than= lthe material of the end portions, and the material of which the end portions are composed having a higher coercive force than the material of the central portion in order to provide a high directing force for the needle. l

2. A compass needle comprising a central portion composed of an alloy comprising iron and 40% to 80% nickel and end portions composed of an alloy comprising 20 to 30% nickel, 6 to 15% aluminum and the remainder iron, thereby obtaining a relatively easy machinability and high permeability in the central portion and high coercive force in the end portions in order to provide a high directing force.

3. A direction-responsive device comprising a damping ring of current-conducting material and a directing element having a central portion composed of a magnetic material and end portions composed of a diiferent magnetic material, the central portion being adapted to be pivoted about a transverse axis and being composed of a softer and more permeable material than the end portions in order to concentrate the leakage ilux in the end portions, the end portions being composed of higher coercive force material than the central portion in order to provide a high directing force for the needle, and said damping ring being coaxial with the pivot axis of and surrounding said directing element for the purpose of damping vibration thereof.

4. An orienting device comprising a center pv oted directing element having a central portion composed of a magnetic material and end portions composed of a different magnetic material, and means actuated by the force of deection of said member, the material of which said central portion is composed being softer and more permeable than that of the end portions, and the material of which the end portions are composed having higher coercive force than the materia] of the central portion in order to provide a high directing force for the directing element.

5. An orienting device for a conveyance comprising a magnetic directing element having a middle portion composed of a magnetic material and end portions composed of a diierent magnetic material, means attached to the middle portion of said directing member for pivoting the same, and means re'sponsive to the deflection of said directing member serving to maintain such conveyance in a predetermined course, the material of which said middle portion is composed being softer and more permeable than that of the end portions, and the material of which the end portions are composed having a higher coercive force than the material of the central portion in order to provide a high directing force for the directing element.

6. An orienting device comprising a central portion composed of magnetic material in sheet form and end portions composed of a. different magnetic material in the form of bars, said central portion being adapted to be pivoted at its center and having lateral projections at its ends bent around the inner ends of said bars, the materialI of which said central portion is composed being softer and more permeable than that of the end portions, and the material of which the end portions are composed having higher coercive force than the material of the central portion in order to provide a high directing force for the directing element.

'7. A direction-responsive device comprising a directing element with a ring composed of electrically conducting material surrounding said directing element, said directing element comprising magnetic material at its central portion and a plurality of pairs of parallel members composed of a different magnetic material at its end portions, the material of which said central portion is composed being softer and more permeable than that of the end portions to concentrate the leakage flux in the end portions, said members constituting the end portions being in contact at their inner ends with said permeable material and being composed of a material havf ing a higher coercive force than said central portion to provide a high directing force for the .directing element, said directing element being adapted to be rotatable about a. pivoted axis coaxial with said ring, whereby vibrations of said directing element are damped with respect to rotation about said pivoted axis and also with respect to rotation about the longitudinal axis of said directing element.

8. A compass needle comprising a central portion composed of a magnetic material and end portions composed of a different magnetic material, the central portion-being softer and more permeable than the end portions, and the end portions being composed of a material having a coercive force exceeding 300 Gilberts per centimeter in order to provide a high directing force for the needle.

HAROLD T. FAUS. 

